Delay fuze for rotating munition



- P. H. MOORE Sept. 1, 1964 Filed June 20, 1963 DELAY FUZE FOR ROTATING MUNITION III Fig 2 INVENTOR P 72104 M 440025 flfl/ M United States Patent 3,146,714 DELAY FUZE FOR ROTATING MUNITION Patrick H. Moore, Eden Prairie, Minm, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Filed June 20, 1963, Ser. No. 289,174 7 Claims. (Cl. 102-856) This invention relates generally to the art of munition fuzing and specifically concerns the design of a time delay fuze for use in a rotating munition or projectile.

Many factors must be considered by the designer of a munition fuze. These factors include reliability, safety, cost, size, and ease of manufacture to name but a few. It is evident that these factors are not independent and in many cases are not compatible. An extremely safe fuze is often too unreliable or too costly, and a highly reliable fuze may be more susceptible to accidental detonation. The job of the designer is to optimize these factors without sacrificing one for the others.

The present invention successfully combines these factors into a time delay fuze which is highly reliable and safe yet is not too large or too costly. Reliability is achieved by utilizing a minimum number of moving parts, none of which are intricate or inherently difficult to install and adjust. The fuze is highly safe in that only a rapid rotation about a normal spin axis can arm the fuze. Ordinary handling or accidental dropping will not effect arming. Even a series of shocks successively applied from different directions is not dangerous since the safety mechanism will not release unless inertial forces are simultaneously applied in opposite directions; a situation occurring only when the munition is rapidly rotated about a predetermined spin axis.

The subject fuze can therefore be used in any grenade, rocket, bomb or projectile which rotates about a predetermined spin axis during flight. The centrifugal force developed by the rotating munition releases the arming mechanism to initiate a pyrotechnic delay train. The resulting detonation can be used to initiate the main explosive in the munition or it may provide a preliminary function such as the jettisoning of a rocket motor.

It is therefore an object of the present invention to provide a munition fuze responsive only to the centrifugal force developed about a predetermined axis of rotation of a rotating munition.

A further object of the present invention is to provide a munition fuze which will perform an arming function at a determinable time after launch.

A still further object of the present invention is to provide a munition fuze which is extremely reliable in operation yet will not detonate if subjected to careless handling.

Another object of the present invention is to provide a mechanical munition fuze having no intricate parts and requiring no presetting operations prior to launch.

These and other objects of the invention will become apparent from the following specification and claims, and from the accompanying drawings, wherein:

FIGURE 1 is a sectional view of the preferred embodiment of the fuze shown in the safe condition and taken along a plane perpendicular to the spin axis of the fuze; and

FIGURE 2 is a similar sectional view showing the fuze in the ignited condition.

Referring now to FIGURE 1 there is illustrated a cross sectional view of the subject fuze. The cross section is taken in a plane which is perpendicular to the axis of rotation of the fuze. The fuze includes a body member 10 in which is formed an elongated cylindrical chamber 12. Chamber 12 includes a pair of closed ends 14 and 16 and lies in the plane perpendicular to an axis of rotation of body 18. Chamber 12 intersects the axis of rotation as indicated at 18. Body member 10 rotates in either a clockwise or a counterclockwise direction about axis of rotation or spin axis 18 as shown by arrow 20. Included within chamber 12 is a delay assembly which includes a tubular housing 22. Housing 22 is free to move longitudinally within chamber 12 from the safe position shown in FIGURE 1 to an armed position as shown in FIGURE 2. The length of housing 22 is approximately three-fourths that of chamber 12. 'The ends 24 and 26 of housing 22 thus always lie on either side of spin axis 18.

Housing member 22 is essentially a closed cylinder having a tubular bore or chamber 28 therein. Mounted firmly within bore 28 at end 26 is an inertial mass 30 which includes a firing pin 32. Inertial mass 30 and firing pin 32 are immovably connected together and thus may be cast or otherwise formed from one piece of metal if desired. A hollow pistion member 34 is located in bore 28 adjacent end 24. In the safe position shown in FIGURE 1, piston member 34 extends from a point adjacent end 24 to a point adjacent spin axis 18. In the ignited position as shown in FIGURE 2, piston member 34 has moved within bore 28 to come in contact with firing pin 32. Piston member 34 is thus freely movable within bore 28 from a position adjacent end 24 to a position in contact with firing pin 32.

Contained within piston member 34 is a pyrotechnic delay element which includes an igniter 36, pyrotechnic delay trains 38 and 48, and a detonator 42. In the ignited position shown in FIGURE 2, firing pin 32 has punctured a thin metal cap 44 to initiate igniter 36. Delay trains 38 and 40, each having different burning speeds, are successively ignited to in turn ignite detonator 42. In the preferred embodiment, igniter 36 is a commercially available substance known as NOL 130. Delay train 38 is Atlantic Research Corporation mixture numher 704 and delay train 40 is lead azide. Detonator 42 is composed of RDX.

Also included within body member 10 are a pair of detents 46 and 48. Detents 46 and 48 are mounted within a second chamber 50 which lies in the same plane perpendicular to spin axis 18 and intersects chamber 12 at spin axis 18 "at right angles to chamber 12. Chamber 58 includes a pair of closed ends 52 and 54. A compressed helical spring 56 is mounted within chamber 50 adjacent end 54 and a compressed helical spring 58 is mounted within chamber 58 adjacent end 52. The diameter of chamber 58 is reduced at 68 and 62 to limit the expansion of springs 56 and 58. Detents 46 and 48 lie between the two springs and are thus biased into contact with each other.

As shown in FIGURE 1, detents 46 and 48 each penetrate a slot 64 which is cut in housing 22. In the safe position shown in FIGURE 1 then, detents 46 and 48 enter opposing sides of slot 64 and mate together in the center of bore 28. The ends of detents 46 and 48 have corresponding hemispherical sections removed in order that the two detents overlap when pushed together. In this mated position, detents 46 and 48 hold housing 22 firmly in the safe position and also separate piston member 34 from firing pin 32.

It is noted that detents 46 and 48 are essentially cylindrical pieces of metal stock. Since they have the same diameter, they are freely movable through slot 64 in either direction. The normal position for the detents is shown in FIGURE 1. If, however, the fuze is dropped so that an inertial force is applied to the detents, one of the springs will be compressed and both detents will move in that direction until the force is removed. When the force is removed, the compressed spring will again drive the two detents into the position shown in FIGURE a 1. Since the two detents are freely movable within slot 64, there is no way in which the fuze can be dropped that will cause the detents to separate and release housing member 22 and piston member 34.

The operation of the fuze is as follows. The munition is launched and a rotation is set up about spin axis 18. As the speed of rotation increases, an increasing centrifugal force is developed which acts outwardly from spin axis 18. The center of mass or centroid of detent 46 is on the opposite side of spin axis 18 from that of detent 48. The centrifugal force thus tends to move the two detents apart. At a predetermined speed of rotation, the centrifugal force acting upon detents 46 and 48 is sufficient to overcome the tension of springs 56 and 58. The two detents thus move apart to the position shown in FIGURE 2 and no longer engage slot 64.

The same centrifugal force that causes the detents to move apart is also applied to inertial mass 36 and to piston member 34. Since inertial mass 30 and piston member 34 are on opposing sides of spin axis 13, the centrifugal force tends to move each member away from the spin axis. Inertial mass 30 and piston member 34 are tied together by housing 22 and therefore must move in the direction toward which the greatest force is applied. The delay mechanism is designed so that the moment of inertia about spin axis 18 of inertial mass 3% is greater than that of piston member 34. When detents i6 and 48 are removed, the delay assembly is driven to the position shown in FIGURE 2 by the resulting greater force acting upon inertial mass 39. The centroid of piston member 34 is located such that when inertial mass 39 impacts with end 14 of chamber 12, the centroid of piston member 34 Will be carried through spin axis 13. The centrifugal force then causes piston member 34 to move rapidly toward firing pin 32. The resultant impact of piston member 34 against firing pin 32 causes the pyrotechnic delay element to ignite.

The operation of the fuze is thus entirely dependent upon the centrifugal force developed by the rotating munition. The centrifugal force first moves the detents outwardly to release housing member 22. The greater moment of inertia about the spin axis of inertial mass 30 causes housing 22 to be driven to the position shown in FIGURE 2. This movement in turn causes piston member 34 to move through spin axis 18 where the centrifugal force again drives piston member 34 into contact with firing pin 32.

In the present embodiment of the fuze, an explosive train 66 is provided between the surface of body member and a point adjacent detonator 42 in the ignited position. When detonator 42 explodes, the explosive flash is carried by train 66 to the surface of body member 10. To improve the propagation between detonator 42 and explosive train 66, a section of housing 22 has been cut away as at 68. The only impedance to the propagation of explosion between detonator 42 and explosive train 66 is the thin shell of piston member 34 surrounding detonator 42 and a thin metal shield 70 which covers the end of explosive train 66.

Certain changes might be incorporated in the design without departing from the invention. For example, the explosive train within piston member 34 could be replaced by electrical contact means. A switch could thus be closed upon arming to initiate a remote explosive. In some situations, the explosive train 66 might not be necessary. In other situations it might be necessary to change the detent structure somewhat. The detents need not be exactly perpendicular to the main chamber nor do they have to be exactly perpendicular to the spin axis. It is only necessary that their centroids be on opposing sides of the spin axis and that a component of centrifugal force be applied equally to each. Some variation in the geometry of the main chamber containing the delay assembly is also permissible. Again it is necessary that sufficient components of centrifugal force are available to carry out the desired function.

From the above description, it will be apparent that I have invented a munition fuze having new and more effective means for utilizing the centrifugal force developed by a rotating munition for arming and firing purposes and for providing safety in handling. Although the form of the invention described herein constitutes a preferred embodiment, it will be understood that changes may be made within the spirit of the invention limited only by the scope of the appended claims.

I claim as my invention:

1. A fuze for a rotating munition wherein centrifugal force is developed, comprising: a body member having therein a cylindrical bore with a longitudinal axis disposed in a plane perpendicular to an axis of rotation of said body member and said munition; said bore intersecting said axis of rotation and having first and second closed ends on opposite sides thereof; a delay assembly located in said bore and movable between an unarmed position at said first end and an armed position at said second end; said delay assembly including a tubular housing having a closed end disposed adjacent said first end of said bore, and an opposite end disposed at a point intermediate said axis of rotation and said second end of said bore in said unarmed position; pyrotechnic delay means movably located in said tubular housing; firing pin means mounted within said tubular housing at said opposite end having a moment of inertia about said axis of rotation greater than said pyrotechnic delay means; said pyrotechnic delay means being movable between a safe position at said closed end of said housing and an ignited position in contact with said firing pin means; spring biased detent means mounted in said body member adjacent said axis of rotation; said housing having slot means formed therein at a point intermediate said pyrotechnic delay means in said safe position and said firing pin means; said detent means engaging said slot means to thereby retain said delay assembly in said unarmed position and to separate said pyrotechnic delay means from said firing pin means in said unarmed position; said detent means being adapted to move outwardly under the centrifugal force developed by the rotating munition to thereby release delay assembly; said delay assembly thereafter being moved to said armed position by said centrifugal force acting upon said firing pin means; the centroid of said pyrotechnic delay means thereby being moved through said axis of rotation to allow the centrifugal force to move said pyrotechnic delay means to said ignited position; and explosive train means mounted on said body member extending from a point adjacent said pyrotechnic delay means in said ignited position to a point on an exterior surface of said member.

2. A fuze for a rotating munition wherein centrifugal forces are developed, comprising: a body member having therein an elongated chamber with a longitudinal axis disposed in a plane perpendicular to an axis of rotation of said body member and said munition; said chamber intersecting said axis of rotation and having first and second closed ends on opposite sides thereof; a delay housing located in said chamber having lateral dimensions closely corresponding to the lateral dimensions of said chamber and being movable between an unarmed position at said first end and an armed position at said second end; said delay housing having a second chamber therein with a closed end disposed adjacent said first end, and an opposite end disposed at a point intermediate said axis of rotation and said second end in said unarmed position; pyrotechnic delay means including detonator means movably located in said second chamber; firing pin means mounted within said second chamber at said opposite end having a moment of inertia about said axis of rotation greater than said pyrotechnic delay means; said pyrotechnic delay means being movable between a safe position at said closed end of said second chamber and an ignited position in contact with said firing pin means; spring biased detent means mounted in said body member adjacent said axis of rotation; and said delay housing having slot means formed therein at a point intermediate said pyrotechnic delay means and said firing pin means in said safe position; said detent means engaging said slot means to thereby retain said housing in said unarmed position and separate said pyrotechnic delay means from said firing pin means; said detent means being adapted to move outwardly under the centrifugal force developed by the rotating munition to thereby release said delay housing; said delay housing thereafter being moved to said armed position under the influence of said centrifugal force acting upon said firing pin means; the centeroid of said pyrotechnic delay means thereby being moved through said axis of rotation to allow said centrifugal force to drive said pyrotechnic delay means to said ignited position.

3. An inertial delay fuze for a rotating munition where in centrifugal forces are developed, comprising: a body member having therein a cylindrical chamber disposed in a plane perpendicular to an axis of rotation of said body member and said munition and having a pair of closed ends; said chamber intersecting said axis at a point intermediate said ends of said chamber; a cylindrical housing member located in said chamber and movable therein from an unarmed poistion adjacent one end of said chamber to an armed position adjacent the other end of said chamber; said housing member having a tubular bore therein and in the unarmed position having a first closed end adjacent one end of said chamber, and a second end at a point intermediate said axis and the other end of said chamber; said housing member having slot means formed therein adjacent said axis in the unarmed position; spring biased detent means mounted in said body member intersecting said axis and extending through said slot means into said tubular bore in said unarmed position; a hollow piston member containing pyrotechnic delay means and detonator means movably located in said tubular bore; and firing pin means mounted in said tubular bore at said second end having a moment of inertia about said axis of rotation greater than said piston member; said piston member being held at said first end of said bore by said detent means in the unarmed position; said detent means being adapted to move outwardly under the influence of the centrifugal force developed by said rotating munition to release said housing member and said piston member; said housing member thereafter moving to said armed position under the influence of said centrifugal force on said firing pin means; the centroid of said piston member thereby being carried through said axis of rotation to allow said centrifugal force to move said piston member into contact with said firing pin means.

4. An inertial fuze for a rotating munition wherein centrifugal forces are developed, comprising: a body member having therein an elongated first chamber with a longitudinal axis disposed in a plane perpendicular to an axis of rotation of said body member and said munition; said first chamber intersecting said axis of rotation and having first and second closed ends on opposite sides thereof; a slider located in said first chamber having lateral dimensions closely corresponding to the lateral dimensions of said first chamber and being movable between an unarmed position at said first end and an armed position at said second end; said slider having an elongated second chamber therein with a closed end disposed adjacent said first end of said first chamber and an opposite end disposed at a point intermediate said axis of rotation and said second end of said first chamber in said unarmed position; a hollow piston member containing pyrotechnic ignition means located in said second chamber; firing pin means mounted within said second chamber at said opposite end and having a moment of inertia about said axis of rotation greater than said piston member; said piston member being movable between a safe position at said closed end of said second chamber and an ignited position in contact with said firing pin means; detent means mounted in said body member intersecting said axis of rotation; and said slider having slot means formed therein at a point intermediate said piston member and said firing pin means in said unarmed position; said detent means engaging said slot means to thereby retain said slider in said unarmed position and to separate said piston member from said firing pin means; said detent means being adapted to move outwardly under centrifugal force developed by the rotating munition to release said slider by said detent means being removed from said slot means; said slider thereafter being moved to said armed position under the influence of said centrifugal force acting upon said firing pin means; the centroid of said piston member thereby being moved through said axis of rotation to allow the centrifugal force to move said piston member to said ignited position.

5. An inertial fuze for a rotating munition wherein centrifugal forces are developed, comprising: a body member having therein an elongated first chamber with a longitudinal axis disposed in a plane generally perpendicular to a spin axis of said body member and said munition and having a pair of closed ends; each of said ends being located at a distance from said spin axis greater than the distance from said spin axis to a central portion of said first chamber; a slider located in said first chamber having a slidable fit therein and being movable between an unarmed position at one end and an armed position at the other end; said slider having an elongated second chamber therein with closed first and second ends disposed on opposite sides of said central portion of said first chamber; a hollow piston member containing pyrotechnic ignition means located in said first end of said second chamber; firing pin means mounted within said second end of said second chamber having a moment of inertia about said spin axis greater than the moment of inertia of said piston member; said piston member being movable between a safe position at said first end of said second chamber and an ignited position in contact with said firing pin means; detent means mounted in said body member adjacent said central portion of said first chamber; and said slider having slot means formed therein at a point intermediate said piston member in said safe position and said firing pin means; said detent means engaging said slot means to retain said slider in said unarmed position and to separate said piston member from said firing pin means; said detent means being adapted to move out of said slot means when exposed to a predetermined centrifugal force developed by the rotating munition to release said slider; said slider thereafter being moved to said armed position under the influence of said centrifugal force acting upon said firing pin means; the centroid of said piston member thereby being moved through said central portion of said first chamber to allow said centrifugal force to move said piston member to said ignited position.

6. An inertial fuze for a rotating munition wherein centrifugal forces are developed, comprising: a body member having therein an elongated first chamber with a pair of closed ends and a longitudinal axis disposed in a plane generally perpendicular to a spin axis of said body member; each of said ends being located at a distance from said spin axis greater than the distance from said spin axis to a central portion of said first chamber; a slider located in said first chamber having lateral dimensions closely corresponding to the lateral dimensions of said first chamber and being movable between an unarmed position at one end and an armed position at the other end; said slider having an elongated second chamber therein with closed first and second ends disposed on opposite sides of said central portion of said first chamber; a piston member containing ignition means located in said first end of said second chamber; firing pin means mounted within said second end of said second chamber having a moment of inertia about said spin axis greater than the moment of inertia of said piston memher; said piston member being movable between a safe position at said first end of said second chamber and an actuated position in contact with said firing pin means; a pair of spring loaded detents mounted in said plane in said body member on opposite sides of said central portion of said first chamber and generally perpendicular thereto; and said slider having a slot cut transversely therethrough at a point intermediate said piston member in said safe position and said firing pin means; said slot having interior dimensions closely corresponding to the exterior dimensions of said detents; said detents being spring biased into opposing sides of said slot and freely movable therethrough to retain said slider in said unarmed position and to separate said piston member from said firing pin means; the centroid of said detents being located on opposing sides of said spin axis thereby said detents being adapted to move out of said slot when exposed to a predetermined centrifugal force developed by the rotating munition to release said slider; said slider thereafter being moved to said armed position under the influence of said centrifugal force acting upon said firing pin means; the centroid of said piston member thereby being moved through said central portion of said first chamber to allow the centrifugal force to move said piston member to said actuated position.

7. A fuze for a rotating munition wherein centrifugal forces are developed, comprising: a body member having therein a first chamber with closed ends and a longitudinal axis disposed in a plane generally perpendicular to a spin axis of said body member; said ends being located at a distance from said spin axis greater than the distance from said spin axis to a central portion of said first chamher; slider means located in said first chamber movable between an unarmed position at one end and an armed position at the other end; said slider means having a second chamber therein with first and second ends disposed on opposite sides of said central portion of said first chamber; a piston member containing ignition means located in said first end of said second chamber; firing pin means mounted within said second end of said second chamber having a moment of inertia about said spin axis greater than the moment of inertia of said piston member; said piston member being movable between a safe position at said first end of said second chamber and an actuated position in contact with said firing pin means; detent means mounted in said body member adjacent said central portion of said first chamber; and said slider means having slot means formed therein at a point intermediate said piston member in said safe position and said firing pin means; said detent means engaging said slot means to retain said slider means in said unarmed position and to separate said piston member from said firing pin means; said detent means being adapted to move out of said slot means when exposed to a predetermined centrifugal force developed by the rotating munition to release said slider means; said slider means thereafter being moved to said armed position under the influence of said centrifugal force acting upon said firing pin means; the centroid of said piston member thereby being moved through said central portion of said first chamber to allow said centrifugal force to move said piston member to said actuated position.

References ited in the file of this patent UNITED STATES PATENTS 1,131,164 Semple Mar. 9, 1915 

1. A FUZE FOR A ROTATING MUNITION WHEREIN CENTRIFUGAL FORCE IS DEVELOPED, COMPRISING: A BODY MEMBER HAVING THEREIN A CYLINDRICAL BORE WITH A LONGITUDINAL AXIS DISPOSED IN A PLANE PERPENDICULAR TO AN AXIS OF ROTATION OF SAID BODY MEMBER AND SAID MUNITION; SAID BORE INTERSECTING SAID AXIS OF ROTATION AND HAVING FIRST AND SECOND CLOSED ENDS ON OPPOSITE SIDES THEREOF; A DELAY ASSEMBLY LOCATED IN SAID BORE AND MOVABLE BETWEEN AN UNARMED POSITION AT SAID FIRST END AND AN ARMED POSITION AT SAID SECOND END; SAID DELAY ASSEMBLY INCLUDING A TUBULAR HOUSING HAVING A CLOSED END DISPOSED ADJACENT SAID FIRST END OF SAID BORE, AND AN OPPOSITE END DISPOSED AT A POINT INTERMEDIATE SAID AXIS OF ROTATION AND SAID SECOND END OF SAID BORE IN SAID UNARMED POSITION; PYROTECHNIC DELAY MEANS MOVABLY LOCATED IN SAID TUBULAR HOUSING; FIRING PIN MEANS MOUNTED WITHIN SAID TUBULAR HOUSING AT SAID OPPOSITE END HAVING A MOMENT OF INERTIA ABOUT SAID AXIS OF ROTATION GREATER THAN SAID PYROTECHNIC DELAY MEANS; SAID PYROTECHNIC DELAY MEANS BEING MOVABLE BETWEEN A SAFE POSITION AT SAID CLOSED END OF SAID HOUSING AND AN IGNITED POSITION IN CONTACT WITH SAID FIRING PIN MEANS; SPRING BIASED DETENT MEANS MOUNTED IN SAID BODY MEMBER ADJACENT SAID AXIS OF ROTATION; SAID HOUSING HAVING SLOT MEANS FORMED THEREIN AT A POINT INTERMEDIATE SAID PYROTECHNIC DELAY MEANS IN SAID SAFE POSITION AND SAID FIRING PIN MEANS; SAID DETENT MEANS ENGAGING SAID SLOT MEANS TO THEREBY RETAIN SAID DELAY ASSEMBLY IN SAID UNARMED POSITION AND TO SEPARATE SAID PYROTECHNIC DELAY MEANS FROM SAID FIRING PIN MEANS IN SAID UNARMED POSITION; SAID DETENT MEANS BEING ADAPTED TO MOVE OUTWARDLY UNDER THE CENTRIFUGAL FORCE DEVELOPED BY THE ROTATING MUNITION TO THEREBY RELEASE DELAY ASSEMBLY; SAID DELAY ASSEMBLY THEREAFTER BEING MOVED TO SAID ARMED POSITION BY SAID CENTRIFUGAL FORCE ACTING UPON SAID FIRING PIN MEANS; THE CENTROID OF SAID PYROTECHNIC DELAY MEANS THEREBY BEING MOVED THROUGH SAID AXIS OF ROTATION TO ALLOW THE CENTRIFUGAL FORCE TO MOVE SAID PYROTECHNIC DELAY MEANS TO SAID IGNITED POSITION; AND EXPLOSIVE TRAIN MEANS MOUNTED ON SAID BODY MEMBER EXTENDING FROM A POINT ADJACENT SAID PYROTECHNIC DELAY MEANS IN SAID IGNITED POSITION TO A POINT ON AN EXTERIOR SURFACE OF SAID MEMBER. 